On 06.07.20 14:36, Justin He wrote: > Hi David, thanks for the comments. See my answer please: > >> -----Original Message----- >> From: David Hildenbrand <david@xxxxxxxxxx> >> Sent: Monday, July 6, 2020 4:03 PM >> To: Justin He <Justin.He@xxxxxxx>; Catalin Marinas >> <Catalin.Marinas@xxxxxxx>; Will Deacon <will@xxxxxxxxxx> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>; Mike Rapoport >> <rppt@xxxxxxxxxxxxx>; Baoquan He <bhe@xxxxxxxxxx>; Chuhong Yuan >> <hslester96@xxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux- >> kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; Kaly Xin <Kaly.Xin@xxxxxxx> >> Subject: Re: [PATCH 1/3] arm64/numa: set numa_off to false when numa node >> is fake >> >> On 06.07.20 03:19, Jia He wrote: >>> Previously, numa_off is set to true unconditionally in dummy_numa_init(), >>> even if there is a fake numa node. >>> >>> But acpi will translate node id to NUMA_NO_NODE(-1) in >> acpi_map_pxm_to_node() >>> because it regards numa_off as turning off the numa node. >>> >>> Without this patch, pmem can't be probed as a RAM device on arm64 if >> SRAT table >>> isn't present. >>> >>> $ndctl create-namespace -fe namespace0.0 --mode=devdax --map=dev -s 1g - >> a 64K >>> kmem dax0.0: rejecting DAX region [mem 0x240400000-0x2bfffffff] with >> invalid node: -1 >>> kmem: probe of dax0.0 failed with error -22 >>> >>> This fixes it by setting numa_off to false. >>> >>> Signed-off-by: Jia He <justin.he@xxxxxxx> >>> --- >>> arch/arm64/mm/numa.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c >>> index aafcee3e3f7e..7689986020d9 100644 >>> --- a/arch/arm64/mm/numa.c >>> +++ b/arch/arm64/mm/numa.c >>> @@ -440,7 +440,8 @@ static int __init dummy_numa_init(void) >>> return ret; >>> } >>> >>> - numa_off = true; >>> + /* force numa_off to be false since we have a fake numa node here >> */ >>> + numa_off = false; >>> return 0; >>> } >>> >>> >> >> What would happen if we use something like this in drivers/dax/kmem.c >> instead: >> >> numa_node = dev_dax->target_node; >> if (numa_node == NUMA_NO_NODE) >> numa_node = memory_add_physaddr_to_nid(kmem_start); >> >> and eventually dropping the pr_warn in >> arm64/memory_add_physaddr_to_nid() ? Would that work? > > Yes, it works. I sent a similar patch [1] before. But seems pmem > maintainer didn't satisfy it. Do you think memory_add_physaddr_to_nid() > is better than numa_mem_id()? Well, it's the somewhat-common way to get a NID for memory hotadd. E.g., - drivers/acpi/acpi_memhotplug.c - drivers/base/memory.c - drivers/hv/hv_balloon.c - drivers/virtio/virtio_mem.c - drivers/xen/balloon.c use it in combination with add_memory_*() Especially, ACPI and virtio-mem use it in case NUMA_NO_NID is detected. -- Thanks, David / dhildenb
